Nitrification inhibitors are useful in reducing nitrogen fertilizer requirement, improving crop yields and quality, reducing nitrogen losses, minimizing environmental pollution and increasing fertilizer use efficiency (Prasad, R. and Power, J. R. 1995. Nitrification inhibitors in agriculture, health and environment. Advances in Agronomy 54: 233-281). Benzotriazole was one of the heterocyclie compounds shown to inhibit nitrification of (NH.sub.4).sub.2 SO.sub.4 in soils. (Mc Carty, G. W. and Bremner, J. M. 1989. Inhibition of nitrification in soil by heterocyclic compounds Biol. Fertil. Soil, 8(3), 204, 1989). Benzotriazole was shown to inhibit nitrification to different extents depending on its concentration and the soil, thus showing its variable potency depending on the soil. Since benzotriazole is known to form complexes with a number of metal ions the variable potency may be due to the variations in metal ion availability in these soils. High metal ion concentrations in soil solution may render benzotriazole ineffective as a nitrification inhibitor. No method is available for overcoming the difficulty.